RT8470 1.2A/1A, Hysteretic, High Brightness LED Driver with Internal Switch General Description Features zz z zz 7V to 30V Input Voltage Range The RT8470 is a high efficiency, continuous mode inductive zz z zz Hysteretic Control with High Side Current Sensing step-down converter, designed for driving single or multiple zz z zz Internal N-MOSFETs with 350m Low R DS(ON) series connected LEDs from a voltage source higher than zz z zz 1A Output Current (For TSOT-23-5 Only) the LED voltage. It operates from an input voltage of 7V to zz z zz 1.2A Output Current (For SOP-8 (Exposed Pad) Only) 30V and employs hysteretic control with a high side current zz z zz Up to 97% Efficiency sense resistor to set the constant output current. zz z zz Typical 5% LED Current Accuracy The RT8470 includes an output switch and a high side zz z zz Analog or PWM Control Signal for LED Dimming output current sensing circuit, which uses an external zz z zz 300Hz On-Board Ramp Generator resistor to set the nominal average output current. LED zz z zz Input Under Voltage Lockout brightness control is achieved with PWM dimming from zz z zz Thermal Shutdown Protection an analog or PWM input signal. zz z zz RoHS Compliant and Halogen Free The RT8470 is available in a small TSOT-23-5 package or a more thermal efficient SOP-8 (Exposed Pad) package. Applications z Automotive LED Lighting Ordering Information z High Power LED Lighting RT8470 z Indicator and Emergency Lighting Package Type z Architectural Lighting J5 : TSOT-23-5 z Low Voltage Industrial Lighting SP : SOP-8 (Exposed Pad-Option 1) z Signage and Decorative LED Lighting Lead Plating System G : Green (Halogen Free and Pb Free) Pin Configurations Note : Richtek products are : (TOP VIEW) RoHS compliant and compatible with the current require- VIN SENSE ments of IPC/JEDEC J-STD-020. 5 4 Suitable for use in SnPb or Pb-free soldering processes. 23 Marking Information LX ADJ GND RT8470GJ5 TSOT-23-5 BS= : Product Code BS=DNN DNN : Date Code 8 VIN GND 2 7 SENSE LX GND RT8470GSP 3 6 GND NC 9 4 ADJ 5 RT8470GSP : Product Number NC RT8470 YMDNN : Date Code SOP-8 (Exposed Pad) GSPYMDNN DS8470-04 August 2011 www.richtek.com 1+ - RT8470 Typical Application Circuit V IN 7V to 30V C IN R S RT8470 optional VIN SENSE D ADJ GND L LX Functional Pin Description Pin No. Pin Name Pin Function SOP-8 TSOT-23-5 (Exposed Pad) 7 1 LX Switch Output Terminal. Drain of internal N-MOSFETs. 3, 8, Ground. The exposed pad must be soldered to a large PCB and 2 GND 9 (Exposed Pad) connected to GND for maximum power dissipation. Dimming Control Input : 4 3 ADJ --- Analog signal input for analog control of PWM dimming. --- PWM signal input for digital PWM dimming. 2 4 SENSE Output Current Sense Terminal. Sense LED string current. 1 5 VIN Supply Input Voltage. 5, 6 -- NC No Internal Connection. Function Block Diagram VIN Regulator Bandgap SENSE UVLO UVLO V CC 1.25V + - LX UVLO Dimming Ramp Gen. GND Dimming + ADJ - www.richtek.com DS8470-04 August 2011 2